The present invention relates generally to weld fixtures or similar-type devices for supporting a workpiece, and more specifically to an improved mounting for such a fixture.
Fixtures for supporting a workpiece and, for example, positioning a workpiece to be welded at a specific location, typically include a bar or generally open framework which is rigidly bolted or pinned at opposite ends in some way to the headstock and tailstock positioners of a supportive device. The workpiece or workpieces are mounted in the fixture, and the fixture is attached to the headstock and tailstock positioning devices. The fixture may then be rotated to permit easy access to the workpieces or to provide precise alignment of the workpieces with an automatic machine such as a robotic welder.
Several problems exist with presently available fixture mountings. The headstock and tailstock positioner center lines must be carefully aligned since any misalignment can cause serious binding problems and render the device nonfunctional. If the headstock and tailstock devices are adjustable vertically, their movement must be precisely in unison, a requirement which greatly increases the cost of the devices which effect the vertical adjustment.
Methods of attaching the fixtures, including bolting or pinning up to eight fasteners at each end of a fixture, are usually awkward and time-consuming. The large amount of hardware which has to be connected between the fixture and the headstock and tailstock positioners is rather cumbersome and difficult to keep organized. Heretofore, there has been no reliable and quick attaching method for securing the weld fixtures to the positioning equipment.
The supportive device is often utilized to precisely position the fixture for an automatic operation such as robotic welding, and a keyway or similar indexing structure is provided at the headstock positioner to assure that the fixture rotates in unison with the positioner. However, there is some keyway backlash which of course is magnified as a workpiece extends radially outwardly beyond the center of rotation of the fixture. This backlash error can adversely affect the accuracy of the automatic operation.
It is therefore an object of the present invention to provide an improved mounting method and apparatus for securing weld fixtures or the like to positioning equipment. It is a further object to provide such a mounting method and apparatus which allows quick and precise attachment of the fixtures to the headstock and tailstock positioners.
It is another object of the present invention to provide an attaching mounting method and apparatus for a fixture which permits rapid changeover of the fixture to the positioner headstock and tailstock devices.
It is yet another object of the present invention to provide an attaching mounting for a fixture which reduces the amount of hardware necessary to secure the fixture to the positioning equipment. It is a further object to provide such a structure which may be simply slipped into position and requires no bolting or pinning. It is still another object to provide such a mounting which can be easily attached to most any fixture and positioner.
It is a further object to provide an attaching mounting for a headstock positioner which reduces backlash error and assures more precise and repeatable positioning of the fixture. It is yet another object to provide such a mounting in combination with a tailstock positioner mounting, wherein the latter precisely locates the fixture linearly.
It is still another object of the present invention to provide a quick attach mounting method and apparatus for securing weld fixtures, including relatively massive fixtures, or the like to positioning equipment wherein precise alignment of the headstock and tailstock center lines is no longer necessary. It is yet another object to provide such a mounting apparatus which permits the headstock and tailstock positioners to be raised and lowered in unison while permitting the headstock and tailstock positioners to become slightly misaligned without causing binding of the fixture.
In accordance with the above objects a quick attach mounting for securing a fixture to positioning equipment includes a ball and socket arrangement associated with the headstock positioner and a pair of grooved rollers associated with the tailstock positioner. The ball is located on the center of rotation of the headstock positioner and a socket is secured to one end of the fixture for receipt onto the ball. On the opposite end of the fixture, a tapered roller is secured on the rotational axis of the fixture. The corresponding tailstock positioner includes a pair of grooved rollers which receive and precisely locate the tapered roller. The ball centers the headstock end of the fixture with respect to the rotational axis of the positioner, while the grooved rollers cradle the tapered roller to locate the tailstock end of the fixture linearly and centrally with respect to the axis of rotation. The headstock positioner includes an arm supporting a second ball radially outwardly from the centrally located ball, and the headstock end of the fixture includes a radially outboard alignment device for receiving the ball and constraining the fixture to rotate precisely in unison with the headstock device. The ball and socket and ball and outboard device permit the headstock end of the fixture to be simply slipped into position, and after the headstock end is positioned, the tapered roller on the tailstock end is lowered onto the grooved rollers of the tailstock positioner to provide automatic alignment of the fixture with the positioning equipment. The mounting arrangement also permits misalignment of the headstock and tailstock positioners without causing any binding or other serious problems with the fixture. Easy attachment of the fixture to the headstock and tailstock positioners with a corresponding reduction of set-up time is provided. No additional mounting bolts or pins are required so that much of the hardware commonly associated with other fixture mountings is eliminated. Since compensation for misalignment of the headstock and tailstock positioners is provided, it is now possible to more effectively and at less cost provide height adjustment for the headstock and tailstock positioners. The radially outboard alignment device reduces the amount of play between the headstock positioner and the fixture for more accurate and repeatable positioning.
These and other objects, features and advantages of the present invention will become apparent to those skilled in the art from the description which follows and from the drawings.